Angular adjustment devices for use in artificial limb manufacture

ABSTRACT

An adjustment means for pre-setting relative angularity between the axes of two parts of an artificial limb or prosthesis comprising wedge shaped discs mutually rotatable about an axis and having inter-engaging eccentric means for imparting a transverse translational movement between the discs upon relative rotation to eliminate variation of axial spacing between the outer surfaces of the discs upon adjustment thereof.

United States Patent May [ 1 June 27, 1972 [54] ANGULAR ADJUSTMENT DEVICES FOR USE IN ARTIFICIAL LIMB MANUFACTURE [72] Inventor: Denis Ronald William May, London, En-

gland J. E. Ranger and Company Limited, London, England Aug. 9, 1971 [73] Assignee:

[22] Filed:

211 App]. No.: 170,098

Related US. Application Data [63] Continuation-impart of Ser. No. 848,865, Aug. 11,

1969, abandoned.

[56] Relerences Cited UNITED STATES PATENTS 3,414,908 12/1968 Waggott et al "3/1 Primary Examiner-Richard A. Gaudet Assistant Examiner--Ronald L. F rinks Attorney-imirie & Smiley [57] ABSTRACT An adjustment means for pre-setting relative angularity between the axes of two parts of an artificial limb or prosthesis comprising wedge shaped discs mutually rotatable about an axis and having inter-engaging eccentric means for imparting a transverse translational movement between the discs upon relative rotation to eliminate variation of axial spacing between the outer surfaces of the discs upon adjustment thereof.

4 Claims, 5 Drawing figures SHEET IN 2 PATENTEUJum m2 m/mvroz 25111.9 7?. w MAY 67 ATToR/YHJ PATENTEnJum m2 3. 671 me SHEET 2 BF 2 AWE/1 r02 psms 1?. w MA) A Tram 5K9 ANGULAR ADJUSTMENT DEVICES FOR USE IN ARTIFICIAL LIMB MANUFACTURE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 848,865, filed Aug. 1 1, 1969 and now abandoned.

BACKGROUND OF THE INVENTION In US. Pat. No. 3,4l4,908 there is described an alignment device in which angular alignment is adjusted by means of at least two discs of wedge shaped cross-section which are relatively rotatable about the axis of the limb and lockable in ad justed position by manually operable threaded means.

An inherent disadvantage lies in the use of plain discs of wedge shaped cross-section, in that relative rotation about their centers to obtain a given tilt automatically entails an alteration in the axial distance between their outer surfaces at the center. 1 This means that any threaded locking means passing through the center of the discs in the normal fashion is either effectively loosened or jammed by an angular adjustment Operation.

SUMMARY OF THE INVENTION According to the invention, an angular adjustment device for use in artificial limb manufacture comprises at least one pair of discs of wedge shaped cross-section located between two surfaces whose mutual inclination is to be adjusted, the discs of each pair being rotatable relatively to each other upon release of axially located threaded locking means, wherein eccentrically located inter-engaging abutment means are provided at the interface of each pair of discs whereby a relative translational movement is generated along that face sufficient to counteract change in the axial distance between the outer surfaces-of the discs otherwise encountered.

The action of the eccentric abutment means is the equivalent of pushing in or retracting one wedge sufficiently to compensate for the increase or decrease of the axial distance referred to.

The preferred form of abutment means to effect the relative translational movement between discs takes the form of a shallow circular eccentric depression in one disc engaged by a complementary eccentric boss on the other disc.

The degree of eccentricity necessary to achieve the desired efiectof constant height in a pair of relatively rotatable discs can be calculated theoretically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an isometric view showing the inner contact face of a disc of wedge shaped crosssection formed with a shallow ec centric boss;

FIG. 2 is an isometric view of a companion wedge-shaped disc showing the inner working face thereof;

FIG. 3 is a cross-sectional view taken axially of an assembly of discs with associated parts of the prostheses;

FIG. 4 is a side elevation of a schematic single pair of discs at maximum tilt, and

FIG. 5 is a schematic side elevation of two pairs of discs of wedge shaped cross-section separated by a flat disc and shown with no tilt.

DETAILED DESCRIPTION OF THE INVENTION Referring first to FIG. 1, a wedge-shaped disc having an axial bore la and an inclined working face lb, has a diameter D and a maximum thickness or height d.

Its wedge angle is shown as and the amount of eccentricity of the shallow boss 2 is designated e.

A companion wedge-shaped disc 3 is shown in FIG. 2 as having an eccentric recess or depression 4 within an inclined working face 3b and concentrically surrounding an opening 3a through the disc 3.

The relationship of the boss and recess may be reversed as shown in FIG. 3, wherein the recess 4' is in the working face lb of the disc 1' and eccentrically surrounding the bore Ia, and the boss 2 is on the working face 3b of the disc 3' concentric with the through opening 3a.

In assembly with the prosthesis, as shown in FIG. 3, the pair of discs 1, I and 3, 3 have their working faces 1b, lb and 3b, 3b engaged with the boss 2, 2 nested within the recess 4, 4'. The pair or pairs of discs are sandwiched between slotted upper and lower end plates 10 and 11 of the prostheses and secured by a bolt 12 extending through the discs and plates as well as a clamp including a socket portion 13 having a through opening 14 and a ball portion 15 having a bore 16.

Whereas, the bore la, la is of a diameter to closely fit the bolt 12, the opening 3a, 3a is of substantially larger diameter than the bolt to permit lateral movement of the disc relative to the bolt.

Referring next to FIG. 4, the disc 1 is shown engaged with the second disc 3, the boss 2 being nested in the recess 4. The discs are at the maximum angle of tilt on the effective radius R. The radius of the central interface between the discs is designated r.

Where r=R-(d-(D/2) tan 0) then e r sin 6.

Lastly referring to FIG. 5, there are shown two pairs of discs 1 and 3, and 5 and 7, separated by a plain disc 9 of thickness t.

Again the efiective radius of tilt is R, the radius of the central interface between discs 5 and 7 is r and the radius of the central interface between discs 1 and 3 is r while the eccentricities are denoted e, and e then e r sin 0 and 2 r sin 0.

It will be clear that alternative eccentric abutment means may be employed, for example, a pin extending from one disc engaged in a groove in its fellow disc.

It will also be apparent that the drawings show exaggerated angles and eccentricities, which in practice are much smaller; the last may be only a few thousandths of an inch in practice.

I claim:

1. An angular adjustment device for interpositioning between two parts of a prosthesis, comprising at least one pair of discs of wedgeshaped cross-section, each pair having a central interface and outer surfaces engageable with parts of the prosthesis which are connected by locking means extending through said discs,

said discs being relatively rotatable about an axis for adjustment of the angle between the prosthesis parts, and interengaging abutment means at said interface and eccentric of said axis to impart relative translational movement to said discs upon relative rotation thereof to maintain a substantially constant axial distance between said outer surfaces of each pair as established by said locking means.

2. An angular adjustment device according to claim 1 in which the extent of eccentricity e of said abutment means is equal to r sin 0 where r is the radius of the central interface between a pair of discs taken from the center of the effective radius of tilt and 0 is the wedge angle of the discs.

3. An angular adjustment device according to claim 1, wherein said interengaging abutment means comprises an eccentric recess in one disc and an eccentric boss on the other disc and nested in said recess.

4. An angular adjustment device according to claim 3 wherein said locking means comprises a bolt and nut, one of said discs having an axial bore joumalled on said bolt, and the other of said discs having an enlarged opening concentric with its eccentric means to permit lateral movement of said disc relative to said bolt.

4. An angular adjustment device according to claim 3 wherein said locking means comprises a bolt and nut, one 0 said discs having aaxial bore joumalled on said bolt, and the other of said discs having a enlarged opening oncentric with its eccentric means to permit laeeral movement of said dis relative to said bolt.

i k k 

1. An angular adjustment device for interpositioning between two parts of a prosthesis, comprising at least one pair of discs of wedge-shaped cross-section, each pair having a central interface and outer surfaces engageable with parts of the prosthesis which are connected by locking means extending through said discs, said discs being relatively rotatable about an axis for adjustment of the angle between the prosthesis parts, and interengaging abutment means at said interface and eccentric of said axis to impart relative translational movement to said discs upon relative rotation thereof to maintain a substantially constant axial distance between said outer surfaces of each pair as established by said locking means.
 2. An angular adjustment device according to claim 1 in which the extent of eccentricity e of said abutment means is equal to r sin theta where r is the radius of the central interface between a pair of discs taken from the center of the effective radius of tilt and theta is the wedge angle of the discs.
 3. An angular adjustment devicE according to claim 1, wherein said interengaging abutment means comprises an eccentric recess in one disc and an eccentric boss on the other disc and nested in said recess.
 4. An angular adjustment device according to claim 3 wherein said locking means comprises a bolt and nut, one of said discs having an axial bore journalled on said bolt, and the other of said discs having an enlarged opening concentric with its eccentric means to permit lateral movement of said disc relative to said bolt.
 4. An angular adjustment device according to claim 3 wherein said locking means comprises a bolt and nut, one o said discs having aaxial bore journalled on said bolt, and the other of said discs having a enlarged opening oncentric with its eccentric means to permit laeeral movement of said dis relative to said bolt. 